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Computer Graphics and Applications, 2004. PG 2004. Proceedings. 12th Pacific Conference on

Date 6-8 Oct. 2004

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Displaying Results 1 - 25 of 52
  • Real-time voxelization for complex polygonal models

    Publication Year: 2004 , Page(s): 43 - 50
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (878 KB) |  | HTML iconHTML  

    In this paper, we present an efficient voxelization algorithm for complex polygonal models by exploiting newest programmable graphics hardware. We first convert the model into three discrete voxel spaces according to its surface orientation. The resultant voxels are encoded as 2D textures and stored in three intermediate sheet buffers called directional sheet buffers. These buffers are finally synthesized into one worksheet, which records the volumetric representation of the target. The whole algorithm traverses the geometric model only once and is accomplished entirely in GPU (graphics processing unit), achieving real-time frame rate for models with up to 2 million triangles. View full abstract»

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  • Intelligent mesh scissoring using 3D snakes

    Publication Year: 2004 , Page(s): 279 - 287
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1345 KB) |  | HTML iconHTML  

    Mesh partitioning and parts extraction have become key ingredients for many mesh manipulation applications both manual and automatic. In this paper, we present an intelligent scissoring operator for meshes which supports both automatic segmentation and manual cutting. Instead of segmenting the mesh by clustering, our approach concentrates on finding and defining the contours for cutting. This approach is based on the minima rule, which states that human perception usually divides a surface into parts along the contours of concave discontinuity of the tangent plane. The technique uses feature extraction to find such candidate feature contours. Subsequently, such a contour can be selected either automatically or manually, or the user may draw a 2D line to start the scissoring process. The given open contour is completed to form a loop around a specific part of the mesh, and this loop is used as the initial position of a 3D geometric snake. The snake moves by relaxation until it settles to define the final scissoring position. This process uses several fundamental geometric mesh attributes, such as curvature and centricity, and enables both automatic segmentation and an easy-to-use intelligent-scissoring operator. View full abstract»

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  • Snaking across 3D meshes

    Publication Year: 2004 , Page(s): 87 - 93
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1339 KB) |  | HTML iconHTML  

    We present a method of moving snake curves over 3D meshes. Our snake is made from the vertices of a triangular mesh, so it never leaves the 3D surface, eliminating any need for mapping on to ID and subsequent remapping on to the 3D mesh. Our snake finds features related to Gaussian curvature, or ridges and valleys. We move each vertex of the snake to one of its neighbor vertices on the mesh, while reducing the energy of the snake, which expresses distance from a feature, by means of a greedy optimization. This is fast enough to support real-time interaction. We handle changes of snake topology using 3D versions of methods originally developed for images. These can handle collisions within the snake, and hence split the snake and find multiple features. We demonstrate the performance of our algorithm on several example meshes, including human faces. View full abstract»

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  • NeuroEnveloping: a transferable character skin deformation technique

    Publication Year: 2004 , Page(s): 77 - 86
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (534 KB) |  | HTML iconHTML  

    We proposed a character skin deformation method, namely neuroEnveloping. The main idea relies on employing artificial neural networks to learn how to synthesize deformable skin from example shapes paired with skeleton postures of a character. Furthermore, having encoded the deformation information in the neural networks, the skinning model can be applied for the deformation of other similar characters. The character skin is decomposed into patches according to a base control mesh which is introduced as a common platform in the proposed framework. The deformation of each patch of the character is controlled by a trained neural network. We devised an effective stitching operator to eliminate discontinuities between neighboring patches. The experimental results show that the proposed approach can generate aesthetically pleasing results at interactive speed. View full abstract»

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  • A progressive refinement approach for image magnification

    Publication Year: 2004 , Page(s): 351 - 360
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (730 KB) |  | HTML iconHTML  

    The rapid growth in computer graphics and digital cameras has resulted in computer users being able to easily produce digital images. As a result, the need to display and print digital images has increased. Nowadays, high-resolution display and printing devices are available to users. Therefore, high-resolution images are needed in order to produce high quality displayed images and high quality prints. However, since high-re solution images are not usually provided, there is a need to magnify the original images. Previous methods on magnifying images have the disadvantage that either the sharpness of the edges cannot be preserved or that some distinct artifacts are produced in the magnified image. In this paper, we present a novel method for doubling the size of images in which the sharpness of the edges is preserved without introducing distinct artifacts in the magnified images. The proposed method consists of two steps, first generation of an initial magnified image and then progressively refining this image to produce a high quality magnified image. The experimental results show that with the proposed method it is possible to produce magnified images of comparable, and in some cases superior, visual quality to those produced using previous methods. View full abstract»

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  • Classification for Fourier volume rendering

    Publication Year: 2004 , Page(s): 51 - 58
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1388 KB) |  | HTML iconHTML  

    In the last decade, Fourier volume rendering (FVR) has obtained considerable attention due to its O(N2logN) rendering complexity, where O(N3) is the volume size. Although ordinary volume rendering has O(N3) rendering complexity, it is still preferred over FVR for the main reason, that FVR offers bad localization of spatial structures. As a consequence, it was assumed, that it is hardly possible to apply ID transfer functions, which arbitrarily modify voxel values not only in dependence of the position, but also the voxel value. We show that this assumption is not true for threshold operators. Based on the theory of Fourier series, we derive a FVR method, which is capable of integrating all sample points greater (or alternatively, lower) than an iso-value T during rendering, where T can be modified interactively during the rendering session. We compare our method with other approaches and we show examples on well-known datasets to illustrate the quality of the renderings. View full abstract»

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  • Perceptually based approach for planar shape morphing

    Publication Year: 2004 , Page(s): 111 - 120
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (594 KB) |  | HTML iconHTML  

    This paper presents an approach for establishing vertex correspondences between two planar shapes. Correspondences are established between the perceptual feature points extracted from both source and target shapes. A similarity metric between two feature points is defined using the intrinsic properties of their local neighborhoods. The optimal correspondence is found by an efficient dynamic programming technique. Our approach treats shape noise by allowing discarding small feature points, which introduces skips in the traversal of the dynamic programming graph. Our method is fast, feature preserving, and invariant to geometric transformations. We demonstrate the superiority of our approach over other approaches by experimental results. View full abstract»

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  • Mesh modelling with curve analogies

    Publication Year: 2004 , Page(s): 94 - 98
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (446 KB) |  | HTML iconHTML  

    Modelling by analogy has become a powerful paradigm for editing images. Using a pair of before- and after-example images of a transformation, a system that models by analogy produces analogous transformations on arbitrary new images. This paper brings the expressive power of modelling by analogy to meshes. To avoid the difficulty of specifying fully 3D example meshes, we use curve analogies to produce changes in meshes. We apply analogies to families of curves on an object's surface, and use the filtered curves to drive a transformation of the object. We demonstrate a range of filters, from simple local feature elimination/addition, to more general frequency enhancement filters. View full abstract»

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  • A versatile interactive 3D brush model

    Publication Year: 2004 , Page(s): 319 - 328
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1509 KB) |  | HTML iconHTML  

    We present a flexible modeling approach capable of realistically simulating many varieties of brushes commonly used in painting. Our geometric model of brush heads is a combination of subdivision surfaces and hundreds of individual bristles represented by thin polygonal strips. We exploit bristle-to-bristle coherence, simulating only a fraction of the bristles and using interpolation for the remainder. Our dynamic model incorporates realistic physically-based deformation, including anisotropic friction, brush plasticity, and tip spreading. We use an energy minimization framework with a novel geometric representation of the brush head to generate a wider variety of brushes. Finally, we have developed an improved haptic model that provides realistic force feedback, directly related to the results of the brush dynamic simulation. Using this model, we are able to simulate a wide range of brush styles and create an excellent variety of strokes such as the crisp, curvy strokes of Western decorative painting, or rough scratchy strokes like certain Oriental calligraphy. We have also developed an exporter for a popular free 3D modeling package that makes it easier for non-programmers to create any desired style of brush, real or fanciful. View full abstract»

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  • Density measure for line-drawing simplification

    Publication Year: 2004 , Page(s): 309 - 318
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1617 KB) |  | HTML iconHTML  

    We present an approach for clutter control in NPR line drawing where measures of view and drawing complexity drive the simplification or omission of lines. We define two types of density information: the a-priori density and the causal density, and use them to control which parts of a drawing need simplification. The a-priori density is a measure of the visual complexity of the potential drawing and is computed on the complete arrangement of lines from the view. This measure affords a systematic approach for characterizing the structure of cluttered regions in terms of geometry, scale, and directionality. The causal density measures the spatial complexity of the current state of the drawing as strokes are added, allowing for clutter control through line omission or stylization. We show how these density measures permit a variety of pictorial simplification styles where complexity is reduced either uniformly, or in a spatially-varying manner through indication. View full abstract»

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  • Interactive caustics using local precomputed irradiance

    Publication Year: 2004 , Page(s): 143 - 151
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (986 KB) |  | HTML iconHTML  

    Bright patterns of light focused via reflective or refractive objects onto matte surfaces are called "caustics". We present a method for rendering dynamic scenes with moving caustics at interactive rates. This technique requires some simplifying assumptions about caustic behavior allowing us to consider it a local spatial property which we sample in a preprocessing stage. Storing the caustic locally limits caustic rendering to a simple lookup. We examine a number of ways to represent this data, allowing us to trade between accuracy, storage, run time, and precomputation time. View full abstract»

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  • Non-photorealistic real-time rendering of characteristic faces

    Publication Year: 2004 , Page(s): 339 - 347
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1958 KB) |  | HTML iconHTML  

    We propose a system for real-time sketching of human faces. On the basis of a three-dimensional description of a face model, characteristic line strokes are extracted and represented in an artistic way. In order to enrich the results with details that cannot be determined analytically from the model surface and anchor strokes are supplemented interactively and are maintained during animation. Because of the real-time ability of our rendering pipeline the system is suitable for interactive facial animation. Thus, interesting areas of application within the range of the virtual avatars are possible. View full abstract»

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  • Adaptive real-time 3D acquisition and contour tracking within a multiple structured light system

    Publication Year: 2004 , Page(s): 361 - 370
    Cited by:  Papers (5)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1374 KB) |  | HTML iconHTML  

    Active 3D acquisition setups currently capture 3D data from a single viewpoint. We propose a system that supports the effective use of multiple structured light modules placed around the object of interest. We show how oppositely positioned modules could work together and how we can avoid those parts of the background that unnecessarily take up computation time. Key to the setup is having the structured light patterns masked outside the outlines of the object to be captured. This is done very fast, so that the system can be used for motion capture. Only off-the-shelf hardware is required. View full abstract»

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  • Controllable single-strip generation for triangulated surfaces

    Publication Year: 2004 , Page(s): 61 - 69
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1719 KB) |  | HTML iconHTML  

    In this paper, we introduce a method to represent a given triangular model using a single triangle strip. Since this problem is NP-complete, we break the limitation by splitting adjacent triangles when necessary. The common edge is split at the mid-point, and the newly formed triangles are coplanar with their parent triangles. Hence, the resulting geometry of the model is visually and topologically identical to the original triangular model. Our method can develop any edge-connected oriented 2-manifold of arbitrary topology, with or without boundary, into a single strip. Our stripification method can be controlled to start and end at triangles incident on specific vertices. Further, an acyclic set of edges of the input model can be marked as "constraint edges" and our method can generate a single strip that does not cross over these edges, but still cover the whole model. View full abstract»

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  • Unlifted loop subdivision wavelets

    Publication Year: 2004 , Page(s): 25 - 33
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1415 KB) |  | HTML iconHTML  

    In this paper, we propose a new wavelet scheme for loop subdivision surfaces. The main idea enabling our wavelet construction is to extend the subdivision rules to be invertible, thus executing each inverse subdivision step in the reverse order makes up the wavelet decomposition rule. As opposed to other existing wavelet schemes for loop surfaces, which require solving a global sparse linear system in the wavelet analysis process, our wavelet scheme provides efficient (linear time and fully in-place) computations for both forward and backward wavelet transforms. This characteristic makes our wavelet scheme extremely suitable for applications in which the speed for wavelet decomposition is critical. We also describe our strategies for optimizing free parameters in the extended subdivision steps, which are important to the performance of the final wavelet transform. Our method has been proven to be effective, as demonstrated by a number of examples. View full abstract»

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  • Pattern oriented remeshing for Celtic decoration

    Publication Year: 2004 , Page(s): 199 - 206
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3067 KB) |  | HTML iconHTML  

    Decorating arbitrary meshes with Celtic knots requires polygonal meshes with regular connectivity and close to regular face geometry. Because these properties are often irregular, especially in scanned or reconstructed models, the Celtic knots produced may be erratic and undesirable. In this paper we remesh models based on planar tilings defined by the user. Such pattern-oriented surfaces allow us to decorate models with attractive Celtic knots in a consistent fashion and may be applicable to a large number of algorithms that are sensitive to mesh structure. View full abstract»

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  • Normal based estimation of the curvature tensor for triangular meshes

    Publication Year: 2004 , Page(s): 288 - 297
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2591 KB) |  | HTML iconHTML  

    We introduce a new technique for estimating the curvature tensor of a triangular mesh. The input of the algorithm is only a single triangle equipped with its (exact or estimated) vertex normals. This way we get a smooth junction of the curvature tensor inside each triangle of the mesh. We show that the error of the new method is comparable with the error of a cubic fitting approach if the incorporated normals are estimated. If the exact normals of the underlying surface are available at the vertices, the error drops significantly. We demonstrate the applicability of the new estimation at a rather complex data set. View full abstract»

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  • Simulation and control of physical phenomena in computer graphics

    Publication Year: 2004 , Page(s): 171 - 173
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (278 KB) |  | HTML iconHTML  

    In computer graphics applications such as feature animation and games there is a need to produce convincing simulations of phenomena such as smoke, water, cloth and rigid bodies. Computational physics is the natural framework for such simulations. The physical equations describing most of these phenomena are well known and have been extensively studied over the last couple of centuries by the physics community. Which solution technique to use in practice depends on the application. In computer graphics it is desirable to have fast and stable simulations. Ideally, the simulations should run in realtime. This is important of course in games but also in movie production houses where animators have to fine tune the parameters of the simulation. On the other hand it is also desirable that these simulations are easy to implement. This makes the code easier to maintain in a commercial system. Our experience has been that good solutions very often result in simple algorithms which are relatively easy to code. This paper mainly focuses on the simulation of fluids such as smoke, water and fire. Our fluid solver which was first introduced in Stam (1999) relies on a spatial discretization of space into voxels. The physical quantities describing the fluid such as velocity and density are assumed to be constant in each voxel. These values are updated over each time step to create an animation of a fluid flow. View full abstract»

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  • Segmentation of 3D meshes through spectral clustering

    Publication Year: 2004 , Page(s): 298 - 305
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (698 KB) |  | HTML iconHTML  

    We formulate and apply spectral clustering to 3D mesh segmentation for the first time and report our preliminary findings. Given a set of mesh faces, an affinity matrix which encodes the likelihood of each pair of faces belonging to the same group is first constructed. Spectral methods then use selected eigenvectors of the affinity matrix or its closely related graph Laplacian to obtain data representations that can be more easily clustered. We develop an algorithm that favors segmentation along concave regions, which is inspired by human perception. Our algorithm is theoretically sound, efficient, simple to implement, andean achieve high-quality segmentation results on 3D meshes. View full abstract»

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  • Dual marching cubes: primal contouring of dual grids

    Publication Year: 2004 , Page(s): 70 - 76
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (839 KB) |  | HTML iconHTML  

    We present a method for contouring an implicit function using a grid topologically dual to structured grids such as octrees. By aligning the vertices of the dual grid with the features of the implicit function, we are able to reproduce thin features of the extracted surface without excessive subdivision required by methods such as marching cubes or dual contouring. Dual marching cubes produces a crack-free, adaptive polygonalization of the surface that reproduces sharp features. Our approach maintains the advantage of using structured grids for operations such as CSG while being able to conform to the relevant features of the implicit function yielding much sparser polygonalizations than has been possible using structured grids. View full abstract»

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  • Modeling hairy plants

    Publication Year: 2004 , Page(s): 217 - 226
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2033 KB) |  | HTML iconHTML  

    The appearance of computer generated plants has improved significantly due to advances in both modeling and rendering. In this paper we describe a system that further improves the appearance of CG plants by including the tiny hairs that cover many plant organs. A plant skeleton is generated using an L-system and graphically interpreted using generalized cylinders. The individual hairs are then mapped onto the surfaces and boundary edges of the mesh. Hair properties are specified and adjusted according to positional information. Sample images included in the paper illustrate the impact of hairs on the appearance of rendered plants. View full abstract»

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  • Swirling-sweepers: constant-volume modeling

    Publication Year: 2004 , Page(s): 10 - 15
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (502 KB) |  | HTML iconHTML  

    Swirling-sweepers is a new method for modeling shapes while preserving volume. The artist describes a deformation by dragging a point along a path. The method is independent of the geometric representation of the shape. It preserves volume and avoids self-intersections, both local and global. It is capable of unlimited stretching and the deformation can be constrained to affect only apart of the model. We argue that all of these properties are necessary for interactive modeling if the user is to have the impression that he or she is shaping a real material. Our method is the first to implement all five. View full abstract»

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  • Hardware-accelerated reconstruction of polygonal isosurface representations on unstructured grids

    Publication Year: 2004 , Page(s): 186 - 195
    Cited by:  Papers (6)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB) |  | HTML iconHTML  

    Volume visualization using isosurface extraction is a well-researched topic. Research demonstrated that even for unstructured grids peak performances of millions of tetrahedra per second can be achieved by exploiting the parallel processing capabilities of modern GPUs. In this paper we present a hardware-accelerated solution that further improves the extraction performance. In contrary to existing approaches, our technique explicitly extracts the isosurface geometry in a fragment program by rendering only a single screen-sized quadrilateral. The extracted geometry is directly written to an on-board graphics memory object allowing for direct rendering without further bus transfers. Additionally, the geometry can be manipulated by shader programs or read back to the application for further processing. Examples and application scenarios are given that can benefit from our approach. View full abstract»

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  • An improved N-bit to N-bit reversible Haar-like transform

    Publication Year: 2004 , Page(s): 371 - 380
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1230 KB) |  | HTML iconHTML  

    We introduce the piecewise-linear Haar (PLHaar) transform, a reversible n-bit to n-bit transform that is based on the Haar wavelet transform. PLHaar is continuous, while all current n-bit to n-bit methods are not, and is therefore uniquely usable with both lossy and lossless methods (e.g. image compression). PLHaar has both integer and continuous (i.e. non-discrete) forms. By keeping the coefficients to n bits PLHaar is particularly suited for use in hardware environments where channel width is limited, such as digital video channels and graphics hardware. View full abstract»

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  • Accelerated geometric queries and physical simulation using graphics processors

    Publication Year: 2004 , Page(s): 37 - 39
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (241 KB) |  | HTML iconHTML  

    Given the increasing power and usage of commodity graphics processor units (GPUs), promising potential exists for exploiting the fast growing computational power on GPUs for general-purpose computing. We present some of our recent research on fast geometric queries and interactive physical simulation using GPUs. View full abstract»

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